OAKLAND — This one hurt to the core of the Raiders. They had lost six times previously this season, but Sunday’s 34-20 defeat to the Kansas City Chiefs touched a nerve.

This one was a hope killer. Reality backhanded the Raiders something fierce, and they were left to stew in the truth they’ve been able to sidestep for a while now.

No, this team was not ready and still is not ready. It was probably too much to expect more from the Raiders than a few more wins and more aesthetically pleasing play.

And after Sunday’s loss, that’s all the Raiders have left to give. Because the playoffs, which were possible in the AFC sludge-fest, are officially a pipe dream. Not because they are mathematically eliminated, but because they have proved again they aren’t ready for that level.

That realization came crashing down on the Raiders, who were put in their place by a beatable but seasoned Chiefs squad.

“We were treating this as our playoffs. We needed to win,” Charles Woodson said. “For us it was a playoff atmosphere. It was a rival. It was the Chiefs. You had your chances and everybody understands what’s at stake at this point.”

And the moment exposed them.

They can’t protect home field. They can’t beat good teams that bring it. They can’t execute like a team worthy of the postseason.

This truth, which has gradually revealed itself before fully surfacing Sunday, shouldn’t taint what the Raiders have accomplished. It should however temper the expectations and hype. This team is on its way somewhere.

But it still has a ways to go. No doubt, that reality is as frustrating as it is reasonable.

Because you can see it’s there. But the leap from being capable to being successful is significant, and the Raiders haven’t made it yet. Clearly, that is too much too soon.

“It’s really hard to win in this league,” Raiders quarterback Derek Carr said, later adding, “No one cares about anything but winning in this league. A lot of things are really good and a lot of things get thrown under the table when you win, so I’d say that’s what we haven’t done yet, is win enough games.”

These Raiders have quite a ways to go despite how far they’ve come. And with that comes the uncertainty of whether they will actually take that next step.

It will require some of their talented young pieces to develop. It will require coach Jack Del Rio’s staff to be better. It will require general manager Reggie McKenzie continuing his streak of good drafts and landing some free agents.

That is a lot that needs to go right for a franchise that is so used to getting it wrong. So Sunday’s loss officially transitioned this season from a celebration of the Raiders being competitive to the anxiety of whether they can take the next step.

The Raiders have lost several games they could have won, even should have won. Is that lack of experience or a hard ceiling?

They are 2-4 at home. Is that a just how it goes when you’re learning how to win in the NFL? Or is it a flaw in the coaching, a snapshot of their core players’ lack of clutchness that will keep them from getting much further than here?

It feels as if this is just a natural part of the process. These feel like the lumps they have to take.

But watching Carr — who became the eighth player to throw for 3,000 yards in his first two seasons — throw three interceptions and look the opposite of clutch against a good defense makes you wonder. Watching the conservatism of the offense, weekly mired in ruts despite its collection of weapons, creates concern these blown games are about ineptitude more than inexperience. Watching the Raiders defense get carved up fosters doubts about whether they will ever get that side of the ball right.

The progress the Raiders made would feel much more legit had they managed to capitalize off their chances. Making the playoffs would have been tangible proof the Raiders have arrived.

But the way this year has gone, it is clear they have not. They are no doubt better. But how much better is still up in the air. And Sunday confirmed just how good they are not.